Device for use in monitoring particulate flow

ABSTRACT

A device ( 10 ) for use in monitoring or measuring properties of a moving bed ( 11 ) of particulate material includes a sled ( 12 ) that rides or floats on the top surface ( 15 ) of the moving bed ( 11 ). A mounting structure ( 14 ) holds the sled ( 12 ) stationary with respect to the linear movement of the particulate bed ( 11 ), but permits movement of the sled ( 12 ) in a direction perpendicular to the movement of the bed ( 11 ), such as up and down when the bed ( 11 ) is moving horizontally. The sled ( 12 ) can carry on board sensors ( 76 ) to monitor the particulate material properties. Other sensors ( 72, 54 ) can be located remote from the sled ( 12 ) such as a sensor ( 54 ) to indicate displacement of the sled ( 12 ) in a direction perpendicular to the direction of travel of the moving bed ( 11 ). In one embodiment, the device includes a flume-like collector that directs particulate material through a sampling cell comprised of parallel side walls ( 47, 48 ) with the sensor sled ( 12 ) located between the sidewalls.

This application claims the benefit of U.S. provisional applicationserial No. 60/178,268 filed Jan. 27, 2000 entitled “Particulate FlowMonitoring Device.”

BACKGROUND OF THE INVENTION

Many manufacturing processes produce granular or particulate productswhere either one or more of the properties of moisture content,temperature, density, and flow rate are important to the process or tothe finished product. By way of example only and not limitation, some ofthese processes include:

1. Drying or cooling of grain, pelleted or extruded feeds, or extrudedhuman foods.

2. Controlling the application of heat sensitive ingredients to cooledfeeds/foods including such things as enzymes, vitamins, and other heatsensitive materials.

3. Drying or cooling of pelleted byproducts made from peat, sawdust,corn gluten or the like.

4. Monitoring and controlling moisture content of sand in concretemixing.

5. Monitoring moisture content of pulverized coal at electric powergenerating plants.

6. Monitoring and controlling moisture content of ingredients enteringfood or feed manufacturing processes.

It is desirable to monitor the particular material property orproperties that are important to the particular process or finishedproduct. It is convenient to monitor these properties “on line” or whenthe material is being conveyed from one location to another, either aspart of the process or expressly for the purpose of monitoring aproperty. Without good on line information about a product or process,automation and quality control are difficult. However, current choicesof equipment for monitoring these parameters on-line are very limited orvery expensive.

SUMMARY OF THE INVENTION

The invention pertains to a device for use in on-line monitoring of oneor more properties of a moving stream of particulate material. Thematerial may be moving by means of a mechanical conveyor such as aconveyor belt or under the influence of gravity, such as in an inclinedchute. The monitoring device includes a sled that rides on top of thestream of moving material. In its most essential form the monitoringdevice includes a sled and a mounting structure. The mounting structuremounts the sled in stationary relationship to the stream of particulatematerial. However, the mounting structure permits the sled to “float” onthe surface of the moving particulate stream, The sled can move up anddown on the top of the stream, or in a direction that is substantiallyperpendicular to the direction of movement of the stream of material.

The sled has a base with a substantially flat bottom or under surface toskim over the surface of the particle stream in sled-like fashion. Thesled has an upwardly sloped upstream edge or bow that faces the oncomingflow of particulate material. This permits the sled to ride on the topsurface of the particle stream with minimal drag.

In a defined channel, the elevation of the sled above the lower surfaceof the process stream is a measure of the depth of the stream. Incombination with the velocity of the particle stream, this isproportional to the flow rate. A measurement device can measure thisdepth dimension. The device can be remote from the sled and mountingstructure, such as a remotely located optical measuring device. Thedevice can be on board the sled or the mounting structure. The devicecan measure the vertical displacement of the sled, or the angulardisplacement of a mounting rod connecting the sled to the mountingstructure.

The sled can carry on board measurement devices to measure otherproperties of the particle stream such as temperature and moisturecontent. A particular sensor can sense dielectric properties of theprocess stream which will be indicative of the moisture content anddensity. The linear velocity of the particle stream can be measuredpermitting a computation of the mass flow rate.

The device can include a flume-like collector to produce a definedprocess stream channel. The collector includes parallel sidewallsstraddling the sled in forming a collector cell. Flow deflectors extendfrom the upstream edges of the parallel sidewalls in a divergentrelationship. The flow deflectors form a funnel-like structure to directthe process stream into the sampling cell. A leveling device can be usedto level the surface of the process stream prior to passing under thesled.

IN THE DRAWINGS

FIG. 1 is a top plan view of a device for use in monitoring particulateflow according to one form of the invention;

FIG. 2 is a side elevational view of the apparatus of FIG. 1 taken alongthe line 2—2 thereof and having portions removed for purposes ofillustration;

FIG. 3 is a front elevational view of the apparatus of FIG. 1 takenalong the line 3—3 thereof;

FIG. 4 is an enlarged sectional view of the base of the sled of theapparatus of FIG. 1 taken along the line 4—4 thereof; and

FIG. 5 is a top plan view of a modification of the invention of FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to the drawings, there is shown in FIGS. 1 and 2 a device foruse in monitoring particulate flow indicated generally at 10. Device 10is installed for use in monitoring one or more properties of a movingbed of particulate material or a process stream 11. Monitoring device 10includes a sled 12 mounted by a mounting structure 14. Mountingstructure 14 holds the sled 12 stationary with respect to movement ofthe process stream 11. Mounting structure 14 permits sled 12 to “float”on the top surface 15 of the process stream 11.

Process stream 11 is comprised of a moving bed of particulate material.In the example shown, the process stream 11 rides on a conveyor belt 17although the particular means of movement of the particulate material isnot an element of the invention. The process stream could be moved byother means such as other mechanical devices, or under the influence ofgravity as in a chute or downspout. The “top” of the process streamrefers to the uppermost surface interfacing with the sled 12. Theopposite surface rides on a conveyor surface such as the conveyor beltshown or a downspout wall. The depth of the process stream is thedifference between the two surfaces.

The sled 12 rides on the top surface 15 of the process stream 11. Themounting structure 14 holds the sled stationary with respect to movementof the process stream but permits free movement of the sled in adirection perpendicular to the movement of the process stream. In thecase of the embodiment shown in FIG. 2, the mounting structure 14permits free movement of the sled up and down as the depth of theprocess stream varies.

Sled 12 has a base 18 with a bottom that is substantially flat or flatenough to enable the base to ride on the top surface of the processstream in sled-like fashion. Sled 12 can optionally have side rails 21,22. An upwardly directed lip or bow 19 is fixed to the upstream edge ofbase 18. Bow 19 is upwardly sloped in a direction facing the oncomingstream. The purpose of bow 19 is to minimize drag on sled 12. Bow 19 isshown as a separate member fixed to the base 18 by a structural members23. Bow 19 could an integral, upwardly curved end of base 18.

Mounting structure 14 includes a pivot arm 25 pivotally connected at oneend to a mounting frame 26 for rotation about a lateral axisperpendicular to the direction of movement of the process stream. Theopposite or lower end of pivot arm 25 is pivotally connected to the sled12. Sled 12 has a pair of laterally spaced apart upright mountingcolumns 27, 29. A pivot rod 30 extends laterally between the mountingcolumns 27, 29. A pivot block 31 connected to the lower end of the pivotarm 25 pivotally connects to pivot rod 30. Pivot rod 30 has a lateralaxis perpendicular to the direction of travel of the process stream 12.

Mounting structure 14 includes a pair of upright mounting posts 33, 34.Carrying blocks 36, 37 secured by set screws 38,39 slidably engage themounting posts 33, 34 for vertical adjustment. An upper pivot rod 41extends laterally between the carrier blocks 36, 37. A fastening block42 is connected to the upper pivot rod 41 for rotation thereon. Thefastening block 42 is connected to the pivot arm 25 for rotation of arm25 on the upper pivot rod 41.

A counterweight assembly is fixed to the upper end of mounting arm 25.The counterweight assembly includes a counterweight 44 adjustably fixedto the upper end of the pivot arm 25 by a set screw 45. Adjustment ofthe position of the counterweight on the arm 25 adjusts the effectiveweight of the sled 12. This allows control of the physical contactbetween the sled 12 and the flowing particulate.

The embodiment of the invention shown in FIGS. 1 through 4 includes acollector with a flume-like mouth for collection of a sample ofparticular material in a sensing cell. The sensing cell is defined by apair of parallel sidewalls 47, 48, parallel to the direction of the flowof the process stream. Sidewalls 47, 48 are poised above the conveyorbelt 17, held in place by suitable fastening structure. Conveyor beltassembly side rails 50, 51 straddle the conveyor belt 17. The sidewalls47, 48 are channel shaped. Right angle fastening brackets 52 secured bynuts and bolts fasten the sidewalls 47, 48 to the conveyor belt assemblyside rails 50, 51.

Flow deflectors form a funnel-type mouth to direct the process streambetween sidewalls 47, 48. Flow deflectors 54, 55 extend upstream indiverging relationship from the upstream edges sidewalls 47, 48. Theflow deflectors can be arranged to intercept a portion or all of theprocess stream for diversion through the sampling area.

A leveling apparatus includes a leveling bar that rides on top of theprocess stream upstream of the sled 12. The leveling bar levels theprocess stream for a uniform depth as it passes under the sled 12. Aleveling bar 57 rides on the top of the process stream and substantiallyspans the width between sidewalls 47, 48. Leveling bar pivot arms 58, 59are connected at one end to the leveling bar 57 and at the other end toa leveling bar pivot rod 61. The ends of pivot rod 61 are rotatablyaccommodated in mounting blocks 63 (FIG. 2) vertically adjustable onmounting posts 65.

FIG. 3 shows mounting clamps 66 connected to upper and outwardly turnedflanges on the sidewalls 47, 48. Clamps 66 support mounting posts 33,34. FIG. 3 also shows a conveyor belt roller 68 that carries theconveyor belt 17. A tachometer, indicated at 69, is connected to a shaft70 of conveyor belt roller 68. Tachometer 69 measures the rotationalvelocity of the roller 68 which can be used to compute linear velocityof the conveyor belt 17. Other suitable devices can be employed tomeasure the linear velocity of the conveyor belt 17.

The device 10 is usable in monitoring certain properties of theparticulate stream. These include volumetric flow rate, moisture contentand temperature. In the instance where the monitored particulate streamdoes not have a consistent cross-section that can be mathematicallydescribed, or if it's depth does not satisfy the minimum requirements ofsensors used, the particulate flow is collected and conditioned. This isdone by the optional collector sidewalls and flow deflectors describedabove.

The depth of the process stream is measured by the vertical displacementof the sensor sled above the conveyor surface. In a defined channel thedepth measurement is proportional to the volumetric flow rate of theparticulate stream. Various measurement devices can be used and areconsidered equivalent so long as the displacement of the sled 12 ismeasured. The measurement devices can be on board the sled or remotefrom it. Tilt sensors, lasers and ultrasonic devices are only someexamples of the types of devices that could be used. A device such as atilt sensor can be used to measure the angular displacement of the pivotarm 25 connected to the sled 12. The drawings show a tilt sensor 72mounted on a platform 73 fixed to the pivot arm 25. A suitable brand oftilt sensor is the Schaevitz AccuStar Tilt Sensor. The tilt sensor 72sends a signal through a cable 74 to a suitable computer/controllerindicated at 75. In combination with a measurement of the linearvelocity of the conveyor belt 17, the volumetric flow of the particulatestream can be calculated.

Sled 12 can carry an array of sensors to measure various properties ofthe particulate stream. As shown in FIG. 4, attached to the base 18 ofsled 12 and indicated generally at 76, is a shielded flat plateproximity/dielectric sensor like that shown and described in U.S. patentapplication Ser. No. 09/366,602, now U.S. Pat. No. 6,249,130incorporated herein by reference.

Sensor 76 is attached to the under surface of base 18 of sled 12. Sensor76 includes a substrate layer 77 formed of printed circuit boardmaterial or like material. A pair of sensing electrodes 79 is located onthe lower surface of substrate 77 in spaced apart relationship. Thesensing electrodes are coplanar and are formed of a conductive materialsuch as a copper film. When current is applied to one electrode,electric field lines are generated to the other electrode.

A first shield electrode 80 is mounted on the side of substrate 77opposite the sensing electrodes 79 and is positioned to intercept orblock electric field lines from extending to the rear or oppositesurface of the sensing element.

A second shield electrode 81 is arranged on the front surface of thedielectric substrate 77 coplanar with and between the sensing electrodes79 and spaced parallel relation between them. The second shieldelectrode intercepts or blocks the field lines that are closest to thesensing electrode in order to prevent the densest portion of theelectric field very near the sensing electrode from severely dominatingcapacitive measurements.

A protective dielectric layer 83 is provided over the sensing electrodes79, the second shield electrode 81 and the remainder of the surface ofthe substrate layer 77. The protective layer 83 interfaces with theparticulate stream 11.

Electric field lines originate from one of the sensing electrodes 79 andterminate at the other. These field lines are forced outwardly into theparticulate stream. The changes in capacitance between the sensingelectrodes is detected or measured. More specifically, the dielectricproperties of the particulate stream are detected and measured. Thedetected signals are used for measuring certain properties of theparticulate stream such as moisture content.

An electrical lead 84 (FIG. 2) extends from sensor 76 to a suitablecomputer/controller 75 for processing.

In the use of the invention, sled 12 is mounted by suitable mountingstructure so as to ride or “float” on the top of a particulate stream.The mounting structure can be comprised of rigid or flexible membersthat attach from either above or beneath the sensor sled. The criteriais that the sensor sled be held stationary with respect to the movingparticulate stream and be permitted to rise and fall according to thevariation of the depth of the particulate stream.

The particle stream flows under the sled 12. The following data can begenerated: vertical displacement of the sled, indicative of volumetricflow rate; particulate temperature; particulate dielectric propertiesindicating the moisture content, density or other such characteristics.The effective weight of the sled can be adjusted to increase contactbetween the sled surface and the monitored flowing particulate materialto improve sensitivity. This can be done through adjustment of thecounterweight 44 on the pivot arm 25 in the embodiment of the mountingstructure shown. Other equivalent means to adjust the effective weightof the sled could be employed.

If the invention is used on a conveyor belt or similar device, a meansfor monitoring the linear velocity of the particulate stream can beused. In the example illustrated, a tachometer mounted on a drive rolleris used.

When desirable, a flume type collector device can be used in order tocreate a mathematically definable channel of particulate matter. Theleveling bar assembly is used to provide a uniformly flat cross-sectionto the particulate flow in a sensing cell defined by the sidewalls 21,22.

FIG. 5 shows an embodiment of the invention without the flume-typecollector. The sled 12 rides on the top of the particulate processstream 11A that is confined between conveyor assembly sidewalls 50,51.Pivot arm 25 rotatable connects the sled 12 to the upper lateral pivotrod 41. Pivot rod 41 is mounted in carrying blocks 36A and 37A that aresecured to mounting posts 33A, 34A. A sample of the particulate streampasses under the sled 12.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A device for use inmonitoring one or more particulate material properties of a moving bedof particulate material on a conveyor surface, comprising: a sensor sledhaving a base with a substantially flat bottom for riding on the top ofmoving bed of particulate material, and an upwardly sloped front wallfor facing upstream relative to the moving bed; a mounting structureconnected to the sled positioning the sled relative to the conveyorsurface to ride on top of the bed with the front wall facing upstream,said mounting structure including a mounting member attached to the sledto hold the sled stationary with respect to linear movement of the bedand permit displacement of the sled in a direction perpendicular to themovement of the bed as the depth of the bed varies on the conveyorsurface; at least one sensor positioned on the sled to measure aproperty of the particulate material.
 2. The device of claim 1 wherein:the mounting member comprises a pivot arm.
 3. The device of claim 2wherein: the mounting structure includes an upper pivot rod extendinglaterally across and above the conveyor surface, said pivot armconnected at an upper end to the upper pivot rod.
 4. The device of claim3 including: a lower pivot rod attached to the sled parallel to theupper pivot rod, said pivot arm connected at one end to the lower pivotrod.
 5. The device of claim 3 wherein: said mounting structure includesa mounting frame having at least one upright mounting post, a mountingblock adjustable attached to the mounting post, said upper pivot rodconnected to the mounting block.
 6. The device of claim 3 wherein: saidmounting structure includes a mounting frame having a pair of uprightmounting posts straddling the conveyor surface, said upper pivot rodconnected between the mounting posts.
 7. The device of claim 3including: an apparatus for measuring the angular displacement of thepivot arm in order to calculate the depth of the bed.
 8. The device ofclaim 7 wherein: said apparatus to measure the angular displacement ofthe pivot arm comprises a tilt sensor mounted on the pivot arm.
 9. Thedevice of claim 1 including: a collector having parallel sidewallsmounted in straddling relationship to the sled and poised above theconveyor surface parallel to the direction of travel of the bed; andflow deflectors extending in divergent relationship from upstream edgesof the sidewalls.
 10. The device of claim 9 including: a leveling barassembly including a leveling bar mounted laterally of the conveyorsurface and upstream of the sled to level particulate material prior toits passing under the sled.
 11. The device of claim 1 wherein: saidsensor includes a dielectric properties sensor.
 12. A device for use inmonitoring one or more properties of particulate material of a movingbed, comprising: a conveyor surface to carry the moving bed ofparticulate material; a sensor sled having a base with a substantiallyflat bottom for riding on the top surface of the bed, and an upwardlysloped front wall for facing upstream relative to the moving bed; amounting structure including an upper pivot rod mounted laterally acrossand above the conveyor surface; said mounting structure including apivot arm connected at one end to the upper pivot rod and at theopposite end to the sled to hold the sled stationary relative to linearmovement of the particulate bed and permit displacement of the sled in adirection perpendicular to the movement of the bed as the depth of thebed varies; and at least one sensor positioned on the sled to measure aproperty of the particulate material.
 13. The device of claim 12wherein: said sensor included a dielectric properties sensor fixed tothe under surface of the base.
 14. The device of claim 13 wherein: saidsled has a second pivot rod parallel to the first pivot rod, said pivotarm connected to the second pivot rod.
 15. The device of claim 14including: a device for measurement of the displacement of the sled fromthe conveyor surface.
 16. The device of claim 15 wherein: the device formeasurement of the displacement of the sled from the conveyor surfacecomprises a tilt sensor mounted on the pivot arm.